October 20, 2014

Almost the entire discussion of e-cigarette toxicity so far has focused on the fact that they expose users to lower levels of carcinogens (cancer-causing chemicals) than conventional cigarettes. At the same time, by design e-cigarettes expose users to nicotine in an aerosol of ultrafine particles that also have direct bilogical effects, particularly on the cardiovascular system and lungs.

Holly Middlekauff and collegaues just published an excellent review on the effects of nicotine and fine particle air pollution (from cigarettes and other sources) in the Journal of the American College of Cardiology that describes how these agents act on the sympathetic nervous system (which controls reflexes) in ways that increase the risk of heart attacks. While they note that there are not yet direct evidence on the effects of e-cigarettes on the sympathetic nervous system, they make a good case for being concerned until people show that such effects are not present.

The paper, "Adverse Effects of Cigarette and Noncigarette Smoke Exposure on the Autonomic Nervous SystemMechanisms and Implications for Cardiovascular Risk," is available here.

Here is the abstract:

This review summarizes the detrimental effects of cigarette and noncigarette emission exposure on autonomic function, with particular emphasis on the mechanisms of acute and chronic modulation of the sympathetic nervous system. We propose that the nicotine and fine particulate matter in tobacco smoke lead to increased sympathetic nerve activity, which becomes persistent via a positive feedback loop between sympathetic nerve activity and reactive oxidative species. Furthermore, we propose that baroreflex suppression of sympathetic activation is attenuated in habitual smokers; that is, the baroreflex plays a permissive role, allowing sympathoexcitation to occur without restraint in the setting of increased pressor response. This model is also applicable to other nontobacco cigarette emission exposures (e.g., marijuana, waterpipes [hookahs], electronic cigarettes, and even air pollution). Fortunately, emerging data suggest that baroreflex sensitivity and autonomic function may be restored after smoking cessation, providing further evidence in support of the health benefits of smoking cessation.

Comments

A research group from the EU Joint Research Centre just published an extensive chamber stuyd analysis of e-cigarette aerosol from several brands that adds to the evidence that e-cigarettes are a substantial source of exposure to nicotine, ultrafine particles, and other chemicals.&nbsp; While the results are similar to earlier work, it adds to the evidence base, particularly that e-cigarette particles are very small.
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The paper is "<strong;Characterisation of mainstream and passive vapours emitted by selected electronic cigarettes</strong;,"http://www.sciencedirect.com/science/article/pii/S1438463914000972";by Otmar Geiss, et al and is available http://www.sciencedirect.com/science/article/pii/S1438463914000972" target="_blank";here.

I notice that the study you link states (rather at odds to your own position)
"Differences in physico-chemical properties (such as solubility) of secondary formed propylene glycol and glycerol droplets, such as those formed during the vaping process, and solid/poorly soluble particles, such as those found in urban areas, have however to be given adequate consideration when evaluating toxicological effects."

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Of particular note,&nbsp;with the Geiss et al data,&nbsp;there are&nbsp;now at least&nbsp;three findings&nbsp;on the topic of significantly raised levels of carbonyls, formed by the thermal decomposition of solvents: the carcinogens Formaldehyde and Acetaldehyde, and the recognised toxins, Acrolein and Acetone.
These are the three papers, including Geiss et al:
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<LI;http://ntr.oxfordjournals.org/content/early/2014/05/14/ntr.ntu078.full";...
<LI;http://link.springer.com/article/10.1007/s00204-014-1294-7";http://link....
<LI;http://www.sciencedirect.com/science/article/pii/S1438463914000972";http...
On the topic of these substances, found in the levels identified, probably the two most prolific physical scientists in the field of electronic cigarette experimentation, Maciej Goniewicz and Konstantinos Farsalinos, have had the following to say.
Maciej Goniewicz, here http://www.prweb.com/releases/2014/05/prweb11874918.htm";http://www.prwe... states that:
&nbsp;“These results suggest that some types of electronic cigarettes might expose their users to the same or even higher levels of carcinogenic formaldehyde than tobacco smoke. Users of high-voltage e-cigarettes need to be warned about this increased risk of harmful effects,”
&nbsp;Dr Farsalinos here http://www.ecigarette-research.com/web/index.php/research/2014/181-who-r... states that:
&nbsp;“the levels of carbonyls emitted from e-cigarettes can (under certain conditions) be similar to or higher than smoking”, and also that
&nbsp;“Of course we continue our research efforts because we need to learn more about e-cigarettes. Of course we are concerned about some issues, such as e-liquid composition (despite the lack of combustion and the absence of cured tobacco) and temperature of e-cigarette use (despite being almost 5 times lower than smoking), not because e-cigarettes may be more harmful than smoking but because we want to find ways to make e-cigarettes even less harmful than they currently are.”
I would respectfully suggest, therefore, that these concerns, raised by these key scientists passionate about the potentials of ENDS, are not raised from a “minor, hypothetical or imaginary” standpoint, as proposed here http://www.clivebates.com/?p=2476#more-2476";http://www.clivebates.com/?... . Significantly, moreover, Dr Farsalinos here http://www.ecigarette-research.com/web/index.php/research/2014/181-who-r... states that:
&nbsp;“Obviously, every non-smoker also deserves to know that the e-cigarette is not a safe new habit for everyone to adopt but a tobacco harm <STRONG;reduction</strong; product. ”
As has been pointed out, as e-cigarette manufacturers <EM;do not limit the sales of their products to current smokers </em;. . . . . . . surely all users AND potential users need to be made&nbsp;aware of these important safety concerns? Misleading comparisons by some between nicotine and caffeine will not help here. Dr Farsalinos has indeed proposed recently a new study on the effects of temperature on fluids herehttp://www.e-cigarette-forum.com/forum/media-general-news/611706-new-e-c...
which&nbsp;I assume he is undertaking, not&nbsp;because of minor, trivial or hypothetical concerns, but because of&nbsp;his previously stated concerns, stated above.
David Bareham